A Bureau of Alcohol, Tobacco, Firearms and Explosives internal affairs letter reveals one of the conflicts that prompted Assistant U.S. Attorney Sue Fahami to tell local ATF agents her office would not prosecute their cases.

Justice Department officials have been mum on the “issues” at the heart of the rift, which idled the Reno ATF office for a year. But the letter states Fahami thought an agent lied to her.

The correspondence was included in a packet sent by Sen. Chuck Grassley to U.S. Deputy Attorney General James Cole. His office is responsible for overseeing the ATF and U.S. Attorneys.

A special agent in the ATF Internal Affairs Division sent a letter on Feb. 10 to the assistant director of the Justice Department’s Office of Professional Responsibility and Security Operations requesting that they close an investigation into Fahami’s allegations.

The agent said the division was notified on Oct. 13, 2011 by the head of the San Francisco Field Division, which oversees Nevada, that Fahami claimed a Reno ATF agent had lied to her about “the presence of a confidential informant during an undercover transaction on a pending criminal case.”

On Dec. 6, 2011, internal affairs special agents interviewed Fahami in Reno with two other federal prosecutors present, the letter said.

It was clear from the interview that there is a “significant communication problem” between the two agencies, the agent said. Those issues should be handled by the new Resident Agent in Charge, who was moving into the Reno office, the agent said.

But the internal affairs agent said nothing that was stated by the federal prosecutors “substantiated the allegation of lies to their office” by the Reno ATF agents.

“There was confusion on how many undercover contacts a particular informant had been present for, and that seemed to stem from the fact that the targets of the investigation were named in two overlapping investigations,” the letter said. “The U.S. Attorney’s office also felt that ATF was not forthcoming in providing information regarding the informant.”

ATF internal affairs agents interviewed Reno agents about the confusion. The agent said he opened one investigation but did not author the report that was called into question by Fahami, the letter said. One of the cases mentioned the informant but the other did not, the letter said.

When the agent was made aware of the informant during the discovery process, he “immediately related that information” to the prosecutor, the letter said.

The agent told the prosecutor that the informant was not signed up by ATF so he could not provide additional information about the person, the letter said. The agent suggested the prosecutor contact the Reno Police Department for more information on the informant, the letter said.

Since nothing supported the allegation of lying and the agent did not write the reports in question, the internal affairs agent asked that the investigation be closed.

No response letters were included in the packet sent to the attorney general’s office.